Heat Shock Factor 1 Governs Sleep-Wake Cycles Across Species.

Heat Shock Factor 1 (HSF1) is a critical transcription factor for cellular proteostasis, but its role in sleep regulation remains unexplored. We demonstrate that nuclear HSF1 levels in the mouse brain fluctuate with sleep-wake cycles, increasing during extended wakefulness and decreasing during sleep. Using CUT&RUN and RNA-seq, we identified HSF1-regulated transcriptional changes involved in synaptic organization, expanding its known functions beyond traditional heat shock responses.

Effect of hemopexin treatment on outcome after intracerebral hemorrhage in mice.

Heme release from hemoglobin may contribute to secondary injury after intracerebral hemorrhage (ICH). The primary endogenous defense against heme toxicity is hemopexin, a 57 kDa glycoprotein that is depleted in the CNS after hemorrhagic stroke. We hypothesized that systemic administration of exogenous hemopexin would reduce perihematomal injury and improve outcome after experimental ICH.

Rapid loss of perihematomal cell viability in the collagenase intracerebral hemorrhage model.

The effective time window of any therapeutic in an experimental stroke model is limited by the rate of injury progression. Intracerebral hemorrhage in rodents is commonly induced by striatal injection of either autologous blood or bacterial collagenase, which digests local blood vessels. During time window studies of the heme oxygenase-1 inducer hemin, which is protective when administered within 1-3 h in both models, the rate of perihematomal injury was directly compared after striatal blood or collagenase injection.

Protective effect of vitreous against hemoglobin neurotoxicity.

Hemorrhage into the brain parenchyma or subarachnoid space is associated with edema and vascular injury that is likely mediated at least in part by the toxicity of hemoglobin. In contrast, extravascular blood appears to be less neurotoxic when localized to the retina or adjacent vitreous, the gel filling the posterior segment of the eye. In this study, the hypothesis that vitreous protects neurons from hemoglobin toxicity was investigated in a primary cortical cell culture model.

Hemopexin increases the neurotoxicity of hemoglobin when haptoglobin is absent.

Hemopexin (Hpx) binds heme with extraordinary affinity, and after haptoglobin may provide a second line of defense against the toxicity of extracellular hemoglobin (Hb). In this series of experiments, the hypothesis that Hpx protects neurons from Hb neurotoxicity was evaluated in murine primary cultures containing neurons and glial cells. Contrary to hypothesis, Hpx increased neuronal loss due to micromolar concentrations of Hb by 4- to 12-fold, as measured by LDH release assay; conversely, the neurotoxicity of hemin was completely prevented.

Astrocyte heme oxygenase-1 reduces mortality and improves outcome after collagenase-induced intracerebral hemorrhage.

Pharmacotherapies that increase CNS expression of heme oxygenase-1 (HO-1) and other antioxidant proteins have improved outcome in experimental models of spontaneous intracerebral hemorrhage (ICH). In order to more specifically investigate the relationship between HO-1 and ICH outcome, mice expressing human HO-1 driven by the glial fibrillary acidic protein (GFAP) promoter (GFAP·HMOX1 mice) were tested in a model of in situ parenchymal hemorrhage. Injection of collagenase into the striata of wild-type (WT) mice resulted in a 26.

Targeting the Nrf2-Heme Oxygenase-1 Axis after Intracerebral Hemorrhage.

Background: Injury to cells adjacent to an intracerebral hemorrhage (ICH) is likely mediated at least in part by toxins released from the hematoma that initiate complex and interacting injury cascades. Pharmacotherapies targeting a single toxin or pathway, even if consistently effective in controlled experimental models, have a high likelihood of failure in a variable clinical setting. Nuclear factor erythroid-2 related factor 2 (Nrf2) regulates the expression of heme oxygenase-1 (HO-1) and multiple other proteins with antioxidant and antiinflammatory effects, and may be a target of interest after ICH.

Haptoglobin increases the vulnerability of CD163-expressing neurons to hemoglobin.

Haptoglobin (Hp) binds hemoglobin (Hb) with high affinity and provides the primary defense against its toxicity after intravascular hemolysis. Neurons are exposed to extracellular Hb after CNS hemorrhage, and a therapeutic effect of Hp via Hb sequestration has been hypothesized. In this study, we tested the hypothesis that Hp protects neurons from Hb in primary mixed cortical cell cultures.

Astrocyte overexpression of heme oxygenase-1 improves outcome after intracerebral hemorrhage.

Background And Purpose: Heme oxygenase-1 (HO-1) catalyzes the rate-limiting reaction of heme breakdown and may have both antioxidant and pro-oxidant effects. In previous studies, HO-1 overexpression protected astrocytes from heme-mediated injury in vitro. In the present study, we tested the hypothesis that selective astrocyte overexpression of HO-1 improves outcome after intracerebral hemorrhage.

Targeting heme oxygenase after intracerebral hemorrhage.

Intracerebral hemorrhage (ICH) is the primary event in approximately 10% of strokes, and has higher rates of morbidity and mortality than ischemic stroke. Experimental evidence suggests that the toxicity of hemoglobin and its degradation products contributes to secondary injury that may be amenable to therapeutic intervention. Hemin, the oxidized form of heme, accumulates in intracranial hematomas to cytotoxic levels.

Neuroprotective effect of heme oxygenase-2 knockout in the blood injection model of intracerebral hemorrhage.

Background: The toxicity of heme breakdown products may contribute to the pathogenesis of intracerebral hemorrhage (ICH). Heme catabolism is catalyzed by the heme oxygenase enzymes. We have previously reported that heme oxygenase-2 (HO-2), the constitutive isoform, protects neurons from hemin in vitro and reduces oxidative stress after striatal blood injection.

Systemic hemin therapy attenuates blood-brain barrier disruption after intracerebral hemorrhage.

Injury to the blood-brain barrier (BBB) is a key feature of intracerebral hemorrhage (ICH) and may contribute to perihematomal cell injury. Pretreatment with the heme oxygenase (HO)-1 inducer hemin improves barrier function and neurological outcome in experimental models of traumatic and ischemic CNS injury. Since hemin is already in clinical use to treat acute porphyrias, this translational study was designed to test its effect on BBB function when initiated after ICH in two mouse models.

Effect of iron chelators on methemoglobin and thrombin preconditioning.

Cell loss immediately adjacent to an intracerebral hemorrhage may be mediated in part by the toxicities of extracellular hemoglobin (Hb) and thrombin. However, at low concentrations, these proteins induce tolerance to hemin and iron that may limit further peri-hematomal injury as erythrocyte lysis progresses. The mechanisms mediating these preconditioning effects have not been completely defined, but increased expression of both heme oxygenase (HO)-1 and iron binding proteins likely contributes.

A rapid fluorescent method to quantify neuronal loss after experimental intracerebral hemorrhage.

Neuronal loss in tissue surrounding an intracerebral hemorrhage (ICH) is usually quantified by labor-intensive histological methods that are subject to bias. Fluorescent protein expression has been successfully used as a marker of cell viability in vitro and in retinal studies in vivo, but not in any ICH model to date. The potential of this approach was investigated using transgenic mice that constitutively express the red fluorescent protein variant dTomato in central neurons under the control of the Thy1 promoter.

Hemopexin decreases hemin accumulation and catabolism by neural cells.

Hemopexin is a serum, CSF, and neuronal protein that is protective after experimental stroke. Its efficacy in the latter has been linked to increased expression and activity of heme oxygenase (HO)-1, suggesting that it facilitates heme degradation and subsequent release of cytoprotective biliverdin and carbon monoxide. In this study, the effect of hemopexin on the rate of hemin breakdown by CNS cells was investigated in established in vitro models.

Iron accumulation and neurotoxicity in cortical cultures treated with holotransferrin.

Nonheme iron accumulates in CNS tissue after ischemic and hemorrhagic insults and may contribute to cell loss. The source of this iron has not been precisely defined. After blood-brain barrier disruption, CNS cells may be exposed to plasma concentrations of transferrin-bound iron (TBI), which exceed that in the CSF by over 50-fold.

Increased striatal injury and behavioral deficits after intracerebral hemorrhage in hemopexin knockout mice.

Object: Heme toxicity may contribute to the pathogenesis of intracerebral hemorrhage (ICH). The primary defense against extracellular heme is provided by hemopexin, a serum and neuronal glycoprotein that binds it with very high affinity and mitigates its prooxidant effect. In the present study, the authors tested the hypothesis that hemopexin knockout mice would sustain more injury after experimental ICH than their wild-type counterparts.

Apotransferrin protects cortical neurons from hemoglobin toxicity.

The protective effect of iron chelators in experimental models of intracerebral hemorrhage suggests that nonheme iron may contribute to injury to perihematomal cells. Therapy with high affinity iron chelators is limited by their toxicity, which may be due in part to sequestration of metals in an inaccessible complex. Transferrin is unique in chelating iron with very high affinity while delivering it to cells as needed via receptor-mediated endocytosis.

Accelerated hemolysis and neurotoxicity in neuron-glia-blood clot co-cultures.

A growing body of experimental evidence suggests that an intracerebral hematoma is toxic to neighboring cells. However, injury mechanisms remain largely undefined, due in part to conflicting results from in vivo studies. In order to investigate blood toxicity in a more controlled environment, murine clots were co-cultured on porous membrane inserts with primary neurons and glia.

Iron regulatory protein-2 knockout increases perihematomal ferritin expression and cell viability after intracerebral hemorrhage.

Iron is deposited in perihematomal tissue after an intracerebral hemorrhage (ICH), and may contribute to oxidative injury. Cell culture studies have demonstrated that enhancing ferritin expression by targeting iron regulatory protein (IRP) binding activity reduces cellular vulnerability to iron and hemoglobin. In order to assess the therapeutic potential of this approach after striatal ICH, the effect of IRP1 or IRP2 gene knockout on ferritin expression and injury was quantified.

Minocycline attenuates iron neurotoxicity in cortical cell cultures.

Iron neurotoxicity may contribute to the pathogenesis of intracerebral hemorrhage (ICH). The tetracycline derivative minocycline is protective in ICH models, due putatively to inhibition of microglial activation. Although minocycline also chelates iron, its effect on iron neurotoxicity has not been reported, and was examined in this study.

Increasing expression of H- or L-ferritin protects cortical astrocytes from hemin toxicity.

Iron toxicity may contribute to oxidative injury in cells surrounding an intracerebral haematoma. Cells detoxify iron by sequestering it in ferritin, a 24-mer heteropolymer constructed of H and L subunits. The relative antioxidant efficacy of H- and L-ferritin has not been defined and was tested in this study using an established model of hemin toxicity.

Heme oxygenase activity and hemoglobin neurotoxicity are attenuated by inhibitors of the MEK/ERK pathway.

Hemoglobin breakdown produces an iron-dependent neuronal injury after experimental CNS hemorrhage that may be attenuated by heme oxygenase (HO) inhibitors. The HO enzymes are phosphoproteins that are activated by phosphorylation in vitro. While testing the effect of kinase inhibitors in cortical cell cultures, we observed that HO activity was consistently decreased by the MEK inhibitor U0126.

Hemoglobin neurotoxicity is attenuated by inhibitors of the protein kinase CK2 independent of heme oxygenase activity.

The heme oxygenase (HO) enzymes catalyze the rate-limiting step of heme breakdown, and may accelerate oxidative injury to neurons exposed to heme or hemoglobin. HO-1 and HO-2 are activated in vitro by the phos-phatidylinositol 3-kinase (PI3K)/Akt and protein kinase C (PKC)/CK2 pathways, respectively. The present study tested the hypotheses that CK2, PKC, and PI3K inhibitors would reduce both HO activity and neuronal vulnerability to hemoglobin in murine cortical cultures.

Iron regulatory proteins increase neuronal vulnerability to hydrogen peroxide.

Iron regulatory protein (IRP)-1 and IRP2 inhibit ferritin synthesis by binding to an iron responsive element in the 5'-untranslated region of its mRNA. The present study tested the hypothesis that neurons lacking these proteins would be resistant to hydrogen peroxide (H(2)O(2)) toxicity. Wild-type cortical cultures treated with 100-300microM H(2)O(2) sustained widespread neuronal death, as measured by lactate dehydrogenase assay, and a significant increase in malondialdehyde.